There has been general documentation and literature on remote sensing, range of methods (radar, optic, infrared, etc. . . . ) sensing equipment and application along with general and specific documentation and literature on environmental application of GIS and the use of GIS/satellite/aerial imagery in the analysis of the built environment. The report of the International Energy Agency (IEA) released in July 2002, entitled Potential for Building Integrated Photovoltaic, Report IEA-PVPS T7-4, discussed the assessment of solar potential on building rooftops. Their methods to assess rooftop surface areas employed gross calculations and was largely inaccurate. According to their method, rooftop surface areas are identified by multiplying the building footprint area by a factor determined by statistical observation of different building stock. Building footprint areas are largely determined by statistical survey of floor area per capita for different building type. The method remains statistical, overlooks the use of GIS technology and fails to recognize and verify the actual conditions in favor of a more abstract rooftop area analysis.
Other papers and reports have been directed to feature recognition coupled with GIS technology. It appears that the field of feature recognition from aerial photographs is still very much in its infancy beyond the range of current solar assessment methods, expertise, and technological capabilities. More accurate assessment methods through the synthesis of a variety of presently available technologies are desired.